Loud-speaker



Oct. 14, 1930.

C. E. SEMFLE .JR

LOUD SPEAKER Filed Feb. 24, 1928 2 Sheets-Sheet l mar/as Z. Jim v16 J oct, 14, 1930.

C E. SEMPLE,. .IR

LOUD SPEAKER Filed Feb. 24, 1928 2 Sheets-Sheet 2 IOU 5 Fly 5 H C/zar/wliemplefi Patented Oct. 14, 1930 UNITED STATES PATENT OFFICE CHARLES a sauna, .m, or CANTON, onro, assrenon T max, Inc, or omen,

01110, A coaronnrrou or 01110 LOUD-SPEAKER Application filed February 24, 1928. Serial No. 256,549.

1 My invention relates to loud speakers for use in the radio, telephone, telegraph, and

other allied arts; and more particularly to a loud speaker including a diaphragm con- 5 nected to the armature of an electro-magnetic sound reproducing unit which may be actuated by relatively weak fluctuating currents. v

If the diaphragm of a loud speaker has a relatively" small area, as for example a circular diaphragm whose diameter is two 'inches, more or less, it may be in the form of a flat disc. The waves emitted by such a small diaphragm are not usually sufiiciently audible, and a horn is usually associated therewith for amplifying to sufficient audibility the sound waves emitted thereby. If the diaphragm of-"a loud speaker is larger in area, it is usually in the form of a cone which itself emits sufficiently audible Waves, and does not require a horn merely v for the purpose of increasing audibility.

For amplifying and facilitating the emission of sound waves applied to large conical 3 diaphragms by electro-magnetic units, some diaphragms have, been made which have been rigidly supported at their peripheries, and which have had a free area equal to that of a circle exceeding 9 inches in diameter. Other diaphragms have been subject to radial tensio'ning. The peripheries of other diaphragms have been yieldingly restrained, without particularly adjusting the force and character of the restraining means. Finally,

3 the peripheries of other diaphragms have been entirely free.

Obviously, the above limitations are mutually contradictory, and loud speakers constructed according to any of them have not been uniformly satisfactory in their reproduction over the full range of audible waves,

nor in the quality of such reproduction, the reproduced. waves frequently being harsh and unpleasant, and there frequently being emitted cracking noises, in addition to the desired Waves, even though the diaphragm be made of non-metallic material such as paper.

. Another important objection to cone type loud speakers constructed according to the foregoing limitations is the fact that in a' diaphragm meeting any of the limitations, a portion of the diaphragm area is doing work other than its intended work of amplifying the vibration applied thereto by the sound reproducing unit. In other words these diaphragms are 'all ineificient.

In a diaphragm rigidly supported at its periphery or to which a radial tension is applied 'a certain proportion of the energy transmitted from the diaphragm to the sound reproducing unit is absorbed-in bending the diaphragm adjacent its periphery, and this bending energy is accordingly not available for amplifying purposes.

In conediaphragms provided with the usual'form ofyielding restraint at its periphery, because each diaphragm is slightly different than others of the same series, and because the restraining means employed have no means of adjustment whatever, and'because in their actual embodiment such restraining means are in fact forms of rigid peripheral supports for the diaphragms,

bending energy is absorbed in a similar manner.

In the case of diaphragms having eutirely free peripheries the air displaced at the periphery tends to swirl from one side of the cone to the other, thereby causing the pe ripheral area of the diaphragm to work against itself, and energy. is wasted because the peripheral portions are thus of no avail for. amplifying purposes.

The horn type loud speakers employing relatively small diaphragms emphasize the higher or treble frequencies, while the cone type loud speakers emphasize the lower or base frequencies. It is desirable that a loud speaker should emit the lower frequencies, but only in a volume permitting audibility of the detail of the higher frequencies. Neither the horn type, nor the cone type loud speakers are satisfactory for-this purpose.

In general, the larger the diaphragm the more readily it will respond to lower frequencies, and the objects of the present improvements include the provision of a loud speaker employing a cone diaphragm larger than the usual horn type loud speaker diaphragm and smaller than the usual free air phragm.

' mediate area,

cone type loud speaker diaphragm. T Such a diaphragm of intermediate. area responds more readily to the higher frequencies, and it is a further object of the presentimprovements' to associate a diaphragm, of intermediate area with other elements in such a manner that the lower frequencies will be emitted therefrom in addition to the higher frequencies which it will emit independently,

without any material reduction in the higher frequencies, all the frequencies being emitted in proper balance with each other, and their quality being soft and pleasing and rela tively free from crackin noises and the like.

'A further object oft e present improvements is to provide a loud speaker including a diaphragm and diaphragm mounting means permitting substantially all of the diaphragm area to be used .for amplifying urposes, thereby increasing the eflic'iency 0 the dia- These and ancillar objects are attained in the loud speaker of the present invention hereinafter set forth in detail, and which may be stated in general terms as including a sound reproducing unit, a conical diaphragm of novel construction and preferably of interand a diaphragm loading the sound-reproducing unit being with the diaphragm for applying chamber, connected "vibrations thereon, and the diaphragm being mounted at its periphery by novel means adapted to provide a highly eflicient diaphragm by applying a yielding variable pressure'on opposite faces of its periphery, and the loading chamber being adapted for applying an air column load on the diaphragm more particularly for amplifying the lower frequency vibrations applied on the diaphragm by the unit, the diaphragm itself being, preferably adequate to sufliciently .amplify the upper frequency vibrations applied by the unit, so that the higher and other. I

A preferred embodiment of the present improvements is illustrated in the accompanying drawings forming part hereof, in which Figure 1 is an elevation view of the im-- proved loud speaker of the present invention,

portions being illustrated in section as on line 11, Fig. 2;

Fig. 2, a top plan view thereof;

ig. 3, an enlarged fragmentary sectional view illustrating the details of the variable yielding mounting for the cone diaphragm periphery;

Fig. 4, a view similar to Fig. 3, illustrating a modified arrangement for the variable yielding mounting; and i Fig. 5, a view similar to F ig.. 1, of a modified embodiment of the improved loud speaker of the present invention.

Similar numerals refer to similar parts throughout the several views.

The improved loud speaker indicated generally at 10 in Figs. 1, 2, and 3, includes a base 11 which may be in the form of a ring 12 having an upwardly extending band 13 from the lower edge of which a flange 141extends outwardly. Legs 15 may support the ring,12 at a suitable distance above the floor, as will hereinafter be s ecified.

The flange 14 is pre erably provided with a plurality of bosses 16, in each of which a socket 17 is formed for receiving one end 18 of a strut '18 which is preferably in the form of a hollow tube, a plug 19 being sweated orv otherwise secured in the end 18 of each tube and provided with a suitable threaded aperture, whereby screws 20 passing through suitable apertures in the flange 14 may be utilized to secure and position the tube struts 18.

The other ends 18 of the tube struts 18 producing unit 25 which may be .of any desired construction.

The upper end 26 of a loading chamber tube 26, preferably made=of paper or plywood, fits within and is secured to the band 22 as by means of screws 27.

The lower end 26 of the tube 26 depends from the band 22 and extends preferably freely through'the band 13, a yielding band 28 of felt 'or the like bein' preferably interposed between the outer ace of the lower end 26 of the tube 26 and the inner face of the band 13. i

A novel conical diaphragm 29 is provided with a laterally extending peripheral flange ring 30, and is associated with the loading chamber tube 26, and the unit 25 preferably by-the following novel means:

An outer pressure ring 31 is provided with apertures through which the shanks of headed screws 32 extend, the upper heads 33 of the screws 32 abutting against theuppersurface of the ring 31, and the shanks of the screws first passing through apertures in an collar 35, then throughapertures in a lower yielding pressure ring 36 of felt or the like, and the lower threaded ends 37 of the screws then being-screwed into suitable apertures in the flange 23 of the angle ring 21.

- The diaphragm peripheral flange 30 is provided, with enlarged apertures through which the collars 35 extend without contacting, and the flange 30 is interposed between the yielding pressure rings 34 and 36 whereby any desired yielding pressure may be 30 by adjustment of the screws 32.

Thediaphragm flange 30 preferably" inade of a suitable fibrous material, which may be leather or the like,.and which is itself rigid enough to support the conical diaphragm 29, which may be made of paper, and maybe provided with a frusto-conical reversely extending base'flange 38 secured at its outer peripheral edge as by gluing or the like to the inner peripheral edge of the diaphragm flange ring 30.

The apex 39 of the cone diaphragm 29. is connected as by means of a link 40 with the armature of the electro-magnetic unit for being actuated thereby. r

The link 40 is preferably rigid in its central portions and flexible at its end connec tion 41 with the cone, and at its end connection 42 with the unit.

The free area of the diaphragm is preferably less than the area of a circle 9 inches in diameter and the length of the loading chamber tube 26 is preferably over 5 inches, the lower end of the loading chamber tube 26 being preferably supported by the legs 15 above the floor a distance substantially equal to the diameter of the tube 26.

As is clearly. illustrated in the drawings, the tube 26 forms a loading chamber for the diaphragm 29 without obstructing either face of the diaphragm.

I By the foregoing construction andarrangement of the improved loud speaker the periphery of the diaphragm is neither rig-- idly secured, nor radially tensioned, but the opposite faces of its peripheral flange may be subject to just the proper amount of yielding pressure to distribute over the entire area of the diaphragm the work of amplifying the vibrations applied thereto by the electromagnetic unit 25. The proper amount of yielding pressure is determined for each par ticular loud-speaker, by a test operator, who has skill similarto that of a piano tuner, and adj u'sts the yielding pressure. until the audible vibrations emitted by the loud speakerare satisfactory to the trained ear of the test operator.

Such distribution of the amplification load is possible neither with a rigidly secured diaphragm periphery, a radially tensioned diaphragm, a free diaphragm periphery, nor a yieldin ly secured diaphargm periphery in which t e yielding securing means is not eX- actly adjustable on opposite faces of the diaphragm periphery. 1

The modified arrangement able yielding mounting illustrated in Fig. 4 is identical with the construction illustrated in Figs. 1, 2, and 3, with the exception that the collar of the modified form consists longitudinally extending end of which a ring flange 123 extends out-- for the variof a coiled compression spring in the place of the solid collar 35.

The improved loud speaker of the foregoing construction including the yielding variable 'pressureapplied upon both faces of the diaphragm periphery, and the loading chamber for the diaphragm formed by the tube 26, emits sound waves, in which the higher and lower frequencies are in proper balance, of suflicient volume in the lower frequencies and suificient detail in the higher frequencies.

The modified embodiment of the improved loud speaker indicated generally at 110 in Fig. 5 includes a base 111 which may be in the form of a ring 112 supported by legs 115 at a suitable distance. above the floor,

as will hereinafter be specified.

The legs 115 preferably intersect at the center of the ring 112, and a boss 116 is formed at the intersection in which a threaded socket 117 is provided for receiving one threaded end 118' of a strut 118 which is preferably in the form of a length of standard pipe.

The other threaded end 118 of the pipe strut 118 is screwed into a threaded aperture in the base A ofa diaphra and unit mounting bracket B which inc udes a diaphragm mounting angle ring 121 which includes a A plurality. of supporting members 124: extend from the' rin 121 preferably inwardly and downwar ly, and at their lower ends are joined to the base A on which is carried an electro-magnetic sound reproducing unit 125 of any desired construction.

The upper end 126 of a loading chamber tube 126, preferably made of paper or plywood, fits within and is secured to the band 122 as by means of screws 127.

The lower end 126 of the tube 126 depends from the band 122 and extends preferably freely throughthe ring 112, a yielding band 128 of felt or the like beingvpreferably in terposed between the outer face of the lower end 126* of the tube 126 and the inner face of the ring 112.

the diaphragm 29 is provided with a laterally extendingperipheral flange ring 130, and is ,associatedwith a loading chamber tube l26 and the unit 125'pref erably by the fol lowing means, similar to the mounting means of the loud speaker 10.

The ring flange 123 is provided with aperband 122 from one A novel conical diaphragm 129 similar to IOU ' a collar 135, then through apertures in an which the collars 135 extend without con-' upper yielding pressure ring 134 of felt or the like, and the upper threaded ends 137 'of the screws then being screwed into suitable threaded apertures in the flange 131 of an ornamental top cover C for the loud speaker.

The diaphragm peripheral flange 130 is provided with enlarged apertures through tacting, and the flange 130 is interposed between theyielding pressure rings 134 and 136 whereby any desired yielding pressure may be applied on the diaphragm peripheral flange 130 by adjustment of the screws 132.

.The diaphragm flange 130 is preferably made of a suitable fibrous material, which may be-leather or the like,'and which is itself rigid enough to support the conical di aphragm 129, which may be made of paper, and may be provided with a frusto-cenical reversely extending base flange 138 secured at its outer peripheral edge as by gluing or the like to the inner peripheral edge of the diaphragm flange ring 130.

The apex 139 of the cone diaphragm 129 is connectedas by means of a link 140 with the armature of the electro-magnet ic unit 125 for being actuated thereby.

The link 140 is preferably rigid its cen- I stantially equal to the diameter of the tube 126.

When the loading chamber tube is made of the preferred material, paper or ply-wood, this material being vibratile is itself vibratcd during operation of the loud speaker, and

sets in motion the air on the outside of the tube as well as on the inside of the tube.

The most desirable results are obtained, when the length of the straight loading chambertube is greater than the diameter of the diaphragm, and preferably the length of the loading chamber tube, as illustrated inFigs.

.1 and 5, should be several times aslo ng as the diameter of the diaphragm, or longer. I claim: i

1. A loud speaker includinga sound reproducing unit, a diaphragm, means mounting thediaphragm at .itsperiphery by applying a yielding variable pressure upon; opposite faces thereof, and theunit being connected with the diaphragm for applying vibrations thereon, and means forming a loading chamber for applying an air column load on the diaphragm without of the diaphragm.

2. loud speaker including a sound reproobstructing either face ducing unit, a diaphragm of an area equal to that of a circle less than nine inches in diam eter, means mounting the diaphragm at its periphery by applying a yielding variable pressure upon opposite faces thereof, and the unit being connected with the diaphragm for applying vibrations thereon, and means forming a loading chamber for applying an air column load on the diaphragm without obstructing either face of the diaphragm.

3. A loud speaker including a base, a strut extending from the base, a diaphragm mounting means supported by the strut, a diaphragm mounted on the mounting means, and a sound reproducing unit connected to the] diaphragm for applying vibrations thereon.

applying an air column load on the diaphragm.

4. A loud speaker including a sound reproducing unit, a diaphragm, means mounting the diaphragm at its peripheryby applying a yielding variable pressure upon opposite faces thereof, and the unit being connected with the diaphragm for applying vibrations thereon. and a tube connected with the-diaphragm periphery for applying an air column load 011 the diaphragm.

5. A loud speaker including a sound reproducing unit, a diaphragm of an area equal to that of a circle less than nine inches in 1 diameter, means mounting the diaphragm at its perpihery by applying a'yielding variable pressure upon opposite faces thereof, and the unit beingconnected with the diaphragm for applying vibrations thereon, and a tube con.- nected with the diaphragm periphery for applying an air column load on the diaphragm. Y

6. A loud speaker including a base, a strut extending from the base, a diaphragm of an area-equal to that of a circle less than nine inches in diameter mounted on the mounting and means forming a loadingchamber for I ios means, and a sound reproducing unit connected to the diaphragm for applying vibrations thereon, and means forming aloading chamber for applying an air column load on the diaphragm. I l

7. A loud speaker including a sound reproducing unit." a diaphragm, the unit being connected with the diaphragm for applying vibrations thereon, a straight tubeassociatecl with the diaphragm for applying an air column load on thediaphragm', one-end of the tube being connected with the diaphragm and the other end of thetube beingopen, and the length of the tube being greater than the diameter of the diaphragm.

8. A loud speakerincluding a sound reproa diaphragm, the unit being connected with the diaphragm for applying vibrations thereon, a tube connected at one end with the diaphragm peripheryfor applv ing an air column load on the diaphragm, the other end of the tube being open, and the ducing unit,

length of the tube being greater thanthe diameter of the diaphragm.

applying van air column load 'on the diaphragm,'one end of the tube being connected .with the diaphragm and theother end of the;

i tube being open, and the-length of the tube v 9. Aloud speaker including a sound reproducingunit, a diaphra the unit/being connected'with the diap r'agm, for applying vibrations thereon, a straight tube 'of vibratile material associated with the diaphragm for being greater than the diameter of the diaphragm,

10. A loud speaker including a sound re:

producing unit, a diaphragm, the unitbeing, connected with the diaphragm for applying vibrations thereon, a tube of vibratile Ina-- nected with the diaphragm and the other end terial connected with the diaphragm periphery for applying an air column load on the diaphragm, one end of the tube being conr of the tube being open; and the length of the tube being greaterthan the diameterof the diaphragm. i

11. A loud speaker including a'sound reproducing unit, a diaphragm of an area equal to thatot' a circleless than nine inches in diameter the unit being connected with the diaphragm for applying vibrations thereon,

a tube associatedwith' the diaphragm for applying an air column load on the diaphragm, one end of the tube being connected with the diaphragm and the other end of the 'tubebeing open, and the length of the tube being greater than the diameter of the diaphragm.

. In testimony that I claim the above, I have hereunto subscribed my name.

CHARLES SEMPLE, J R. 

